The rate of reduction of iron oxides dissolved in calcium-silicate slags by iron-carbon melts is an important factor in ironmaking and steelmaking processes in general and, in particular, in in-bath smelting steelmaking processes. It has been reported that the rate of metal production during in-bath smelting processes increases with increased slag volume in the smelter. The CaO-SiO.sub.2 -Al.sub.2 O.sub.3 -FeO slag in an in-bath smelting vessel also contains gases, solid carbon, and metal droplets. An analysis of metal production rates in a 170 ton in-bath smelting reactor revealed that the reaction rates at the interfaces of slag-droplet and slag-carbon are equal to those at metal-slag interface [T. Ibaraki, M. Kanemoto, S. Ogata, H. Katayama, and H. Ishikawa: Steelmaking Conference Proceedings, Vol. 73, 1990.] Thus, the Fe-C droplets in the slag phase play an important role during the bath smelting of iron oxides and, therefore, understanding the reactions at the droplet interface is crucial.
There have been several studies in the past investigating the behavior of Fe-C droplets in the slags. The reduction rates of FeO dissolved in CaO-SiO.sub.2 -Al.sub.2 O.sub.3 slags by Fe-C droplets have been experimentally determined by Sawada [Yasushi Sawada: M. S. Thesis, Massachusetts Institute of Technology, Cambridge, 1990.] The important observation from these previous investigations is that there were two distinct regimes of reaction rates--one very fast and other very slow. The faster rates were observed in the initial period of the reaction and the period lasted between 60 to 300 sec. depending on the slag composition and temperature. This faster reaction was found to be zeroth order with respect to carbon in the droplet. The reaction rate in the second stage was very slow and the reaction virtually stopped when carbon in the droplet reached a particular level (approximately 2 wt %).
As a result, the reduction reaction is unable to go to completion leaving slag with FeO and Fe-C, which creates a relatively high carbon intermediate. Additional processing conventional in iron and steelmaking processes must be employed to convert the high carbon intermediate. This appears to be a rate limiting step which directly affects the production of metal (iron) and its subsequent conversion to steel. The prior art does not suggest how the reduction reaction can be forced to completion or how to increase the rate of reaction.
Accordingly, an object of the present invention is to develop a process to increase the rate of the reduction of iron oxides taking place in a FeO containing slag.
Another object is to completely remove carbon from the iron-carbon droplet resulting in the direct production of steel (low carbon iron).